Archean metavolcanics from the Rouyn–Noranda district, Abitibi Greenstone Belt, Quebec. 2. Mobility of trace elements and petrogenetic constraints

Abstract

Qualitative evaluation of altered mafic pillows from the Rouyn–Noranda district of the Abitibi metavolcanic belt reveals that, for low-grade metamorphism, the high field strength elements (HFS: Zr, Y, Ti) and the rare earth elements (REE) are immobile. However, where alteration is extreme, the REE elements are leached and redeposited by carbonate-rich and K-rich metasomatic fluids whilst Zr/Y and Zr/Ti remain unchanged. Rubidium, Ba, and, to a lesser extent, Sr are mobile at all levels of alteration. However, provided certain filters are applied, the original geochemical values of the lavas for the alkaline elements, the HFS elements, and the REE can be defined.The geochemical variations thus identified for the volcanic series of the Rouyn–Noranda district are ascribed to a combination of contamination and fractional crystallization of a primitive tholeiitic magma.